Wireless communication systems commonly include information carrying modulated carrier signals that are wirelessly transmitted from a transmission source to one or more receivers within an area or region.
FIG. 1 shows a prior art wireless cellular array system. The cellular array system of FIG. 1 includes clusters of cells with a base station transceiver at the center of each cell. A first cluster (high-lighted) includes a first base station transceiver 110, a second base station transceiver 120 and a third base station transceiver 130. The first base station transceiver 110 is included within a first cell, and includes sectors designated as 1, 2 and 3. The second base station transceiver 120 is included within a second cell, and includes sectors 4, 5 and 6. The third base station transceiver 120 is included within a third cell, and includes sectors 7, 8 and 9.
The sectors 1, 2, 3, 4, 5, 6, 7, 8 and 9 each include unique transmission channels. That is, the transmission characteristics of information signals from the base station transceivers 110, 120, 130 within each sector is unique from the transmission characteristics of the other sectors within the first cluster. For example, the transmission frequency in sector 1 can be at a first frequency, whereas the transmission frequencies of the other sectors include different transmission frequencies. The transmission channels can be uniquely defined by transmission frequency, transmission time, transmission code or any other transmission technique that includes independent transmission channels.
The prior art cellular array systems generally include clusters being repeated. Therefore, the transmission characteristics of each cluster are repeated. The process of repeating transmission frequencies by repeating clusters is generally termed frequency re-use.
A limitation of repeating transmission characteristics is that the cellular array system suffers from co-channel interference. Each cluster within the cellular array system includes the same set of transmission channels having common transmission characteristics as every other cluster within the cellular array system. Therefore, interference occurs between common transmission characteristic cells of different clusters, causing co-channel interference.
To optimize frequency spectrum allocations, frequency re-use cellular array systems repeat transmission frequencies from cluster to cluster. The amount of co-channel interference between cells of neighboring clusters determines how frequently the transmission frequencies can be re-used, and how close cells having common transmission characteristics can be located.
Receivers within a given sector of the prior art cellular array systems receive information signal from a corresponding base station transceiver. For example, a first receiver 140 within the first sector 1 generally receives only information signals from first base station transceiver 110. A second receiver 150 within the sixth sector 6 generally receives only information signals from the second base station transceiver 120. A third receiver 160 within the eighth sector 8 generally receives only information signals from the third base station transceiver 130.
The ability of wireless systems to transmit information between transmitters and receivers is made difficult by inherent characteristics of the propagation of the transmitted signals through the surrounding environment. The transmitted signals travel along multiple paths before reaching a receiving antenna. The transmitted signals experience different levels of attenuation and propagation delays due to terrain and signal reflections. The attenuation and propagation delays are dependent on the frequency of the transmitted signals. The result is a communication channel that exhibits fading and delay spread.
It is desirable to have an apparatus and method that provides a cellular wireless communication system that can provide enhanced information transmission capacity, minimize the effects of fading, while allowing for re-use of information carrying signals having common transmission characteristics.